Publikationer från Linköpings universitet
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Reoccurring science identities : Swedish secondary students’ interest in scienceand technology compared 2003 and 2020
No full textThis paper examines Swedish secondary students’ interest in science and technology from a gender perspectivein a comparative research design using quantitative data collected 2003 and 2020. National datahas been collected from 610 15-year-old students in 2020 as part of a large-scale comparative researchproject, the Relevance of Science Education - Second (ROSES) and compared with data from the Relevanceof Science Education (ROSE) study from 2003. The results empirically update the research field and showa reoccurring interest pattern with minor changes. Content related to space and unexplained phenomenaare still ranked as interesting to learn about. Girls are interested in health issues and the human body,space, dreams and the human soul. Boys favour items about space, inventions and discoveries togetherwith ABC weapons. Minor developments are that interest in learning about diets and exercise as wellas technology has declined. The least interesting things to learn are almost the same as in 2003, with several topics connected to the national science curriculum. The character of students’ interest in S&T isframed and discussed using the theoretical approach of science identity. The stable character with minorchanges is discussed as reoccurring science identities interpreted by the differentiation hypothesis of the“person-object theory of interest”. Gender differences are interpreted as collective identities shown to be‘domain specific’ not ‘subject specific’ and the content level of analysis provide specificity to ‘interest patterns’which has not been well described earlier in the research literature. Research consequences of thisconceptualization and implications for school practice is critically discussed. A research implication fromthis conceptualization is the importance for future studies to investigate varieties of collective identities
Data-driven Reflectance Acquisition and Modeling for Predictive Rendering
No full textRecent developments in computer graphics, and particularly within predictive rendering, have enabled highly realistic simulations of object appearances. While physically-based reflectance (PBR) models offer widespread utility, measured material reflectance data yields significantly higher accuracy through the direct empirical observation of complex light-scattering interactions. Nevertheless, acquiring and modeling reflectance data entails substantial computational overhead. This thesis investigates data-driven approaches to improve the acquisition, representation, and rendering of reflectance data, with a focus on predictive rendering to achieve precise and reliable visual simulations. The first part of the thesis focuses on acquisition of Bidirectional Reflectance Distribution Function (BRDF) and Spatially Varying BRDF (SVBRDF)—functions that describe light-surface interactions at each point based on incoming and reflected light directions. Lightweight setups are initially explored to enable efficient SVBRDF capture; however, their accuracy falls short for predictive rendering applications, motivating the adoption of gonioreflectometer-based setups. To improve measurement efficiency of such setups, a compressed sensing framework is introduced, which incorporates a deterministic sampling strategy. Additionally, a unified formulation for sparse BRDF acquisition is presented, allowing for the adaptation of sampling patterns and sample counts to the unique properties of each material. This approach significantly enhances reconstruction quality while preserving the same sampling budget. The second part of the thesis addresses modeling of reflectance measurements, particularly the Bidirectional Texture Function (BTF) and BRDF. Sparse representation techniques applied to existing BTF datasets prove effective in compressing texture data while enabling real-time rendering of the measured BTFs. Despite these advances, a discrepancy often arises between model-space errors introduced during approximation and the image-space errors perceived in rendered outputs. To bridge this gap, a systematic psychophysical experiment is performed to analyze the impact of BRDF modeling techniques on rendered material quality. Building on these findings, a neural metric is developed to evaluate perceptual accuracy directly in BRDF-space. This metric exhibits strong correlation with subjective human evaluations and presents the potential to guide BRDF fitting algorithms toward solutions that produce visually accurate and compelling renderings of real-world materials
Correction: Biscoumarin-containing acenes as stable organic semiconductors for photocatalytic oxygen reduction to hydrogen peroxide (vol 5, pg 20780, 2017)
No full textElectrochemical Doping for Absorption and Conductivity Tuning of P(NDI2OD-T2) Films
No full textElectrochemical doping of thin films of poly{[N,N '-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5 '-(2,2 '-bithiophene)} (P(NDI2OD-T2)) is shown as straightforward method to achieve different degrees of doping both during in situ electrochemical experiments as well as in the solid state. Results obtained from cyclic voltammetry and absorption spectroscopy upon reduction can be explained by the presence of the neutral state as well as polaron and bipolaron species, including neutral/polaron and polaron/bipolaron mixed valence states. The UV-vis-NIR spectra are analyzed and explained based on the calculated electronic structure and the corresponding transitions between different states, this includes features such as numbers and positions of the peaks and their evolution during reduction. Most intruingly, doped films are stable after transfer in the solid state, as evidenced by absorption spectroscopy. Conductivity measurements of films with different degrees of doping show a bell-shaped conductivity profile, which underlines the classification of P(NDI2OD-T2) as a conjugated redox polymer with mixed valence transport. Maximum conductivities of up to 2 x 10-4 S cm-1 are obtained at intermediate doping levels under the coexistence of neutral state and polarons. Conductivity measurements of blade-coated films point to anisotropic charge transport with the highest charge transport along the blade /polymer chain direction and an anisotropic conductivity ratio of 4.1.Funding Agencies|Deutsche Forschungsgemeinschaft [GRK2498]; Deutsche Forschungsgemeinschaft (DFG) [SRG/2021/002169]; Department of Chemical Engineering, BITS Pilani, Pilani Campus [2022-06725]; Swedish Research Council</p
Metal-like ductility and high hardness in nitrogen-rich HfN thin films by point defect superstructuring
No full textThe strength of refractory ceramics is much limited by their brittleness. Counterintuitively, we observe simultaneous high hardness and metallic-like ductility in highly overstoichiometric single-crystal HfN1.22 and HfN1.33 films grown by ion-assisted reactive magnetron sputtering. Here, we show by electron microscopy, diffraction methods, and ab-initio calculations the existence of a superstructure ordering of metal vacancies and nitrogen interstitials into sub-nanometer hyper-overstoichiometric and quasi-stoichiometric domains that self-organize into a checkerboard pattern superimposed onto the NaCl-structured lattice. A high intrinsic dislocation density and low dislocation nucleation barrier on {111} &lt; 011&gt; slip systems enable extraordinary ductility and strain hardening at &gt;50% strain, in room temperature uniaxial compression of HfN1.22 micropillars. The films simultaneously exhibit a high hardness - tunable up to 28 GPa via control of stoichiometry - and a remarkable fracture resistance due to dislocation-mediated stress dissipation. The presented findings provide a route for synthesizing nitride superstructured films with unique hardness/toughness combinations.Funding Agencies|Linkoping University</p
Conceptual model for aligning construction logistics capacity through simulation
No full textThe flows of materials arriving at, and waste moving out of a site, require detailed planning for smooth logistic processes. This is underscored by the temporal and spatial limitations around sites, characterized as a pure bottleneck. This paper proposes a conceptual data framework for developing digital twins for logistics capacity planning in construction to align the capacities for (i) incoming materials, (ii) on-site material handling, and (iii) material dispatching from the site. The framework is tested based on quantitative mapping of transport arriving, departures, and movements on-site, from two real-world planned projects. This mapping is then used for testing construction site layout planning (CSLP) scenarios of capacity dimensions through simulations. Ultimately, this paper proposes a first step to integrate transport plans in CSLP. Practitioners can use the model for planning sites for smooth material flows and properly dimensioning loading and unloading area capacities to avoid bottlenecks in logistic operations.Funding Agencies|Swedish Innovation Agency (Vinnova) [2023-00519]</p
Translation and validation of the Swedish version of the EORTC LMC-21, the disease-specific questionnaire for assessing health-related quality of life in patients with colorectal liver metastases
No full textPurposeThe aim of this study was to translate the health-related quality-of-life questionnaire EORTC QLQ-LMC21 into Swedish and to test its clinical and psychometric reliability and validity in patients with liver metastases from colorectal cancer (CRC) undergoing surgical treatment.MethodsThe Swedish versions of the EORTC QLQ-C30 and EORTC QLQ-LMC21 were administered to 250 patients with liver metastases from CRC in four Swedish hospitals before and 3 months after surgical treatment. Psychometric validation of the questionnaire&lt;acute accent&gt;s structure, reliability, and convergent and divergent validity was performed.ResultsData from 242 (97%) patients were suitable for analysis. The QLQ-LMC21 was found to be sensitive to changes over time. Cronbach&lt;acute accent&gt;s alpha coefficient indicated good internal consistency, ranging from 0.84 to 0.89. Test-retest reliability was evaluated in 120 patients (49%), and the intraclass correlation coefficient (ICC) indicated good reproducibility, ranging from 0.67 to 0.93. Convergent and discriminant validity were demonstrated adequately in the multitrait scaling analysis. There were weak correlations between the QLQ-C30 and QLQ-LMC21, which confirms that the health problems addressed by the QLQ-LMC21 are different from those addressed by the QLQ-C30.ConclusionsThe Swedish version of the EORTC QLQ-LMC21 proved to be a valid and reliable questionnaire to use in conjunction with the EORTC QLQ-C30.Funding Agencies|Linkoping University</p
"We can't do everything ourselves."- Why Swedish municipalities deliberately promote intermediation in governing the mobility transition
No full textLiterature on intermediation in transitions has emphasised the importance of publicly promoting intermediation. To understand what drives authorities to financially promote intermediation, we conducted an exploratory study of 16 Swedish municipalities promoting an intermediary actor in the mobility transition, applying the framework of drivers of collaborative governance. The results highlight drivers common to most municipalities, including among others administrators' awareness of collaboration challenges, or their inability to conduct intermediary activities on their own. However, the results also reveal diversity and context dependency of the drivers, leading to municipalities voicing diverse and partly conflicting expectations towards the intermediary. These findings underline the importance of understanding the promotion of intermediation through municipalities as a transactional and personal relationship between administrators and intermediaries. They also underline the relevance of "affective work" to mitigating conflicts caused by the diversity of expectations facing intermediaries, and the importance of municipalities in shaping local ecologies of intermediation.Funding Agencies|Swedish energy agency through the project "Effective regional collaboration for a fossil-free society (VERSAM) [P2022-00149]</p
When Do Trait-Based Higher Order Interactions and Individual Variation Promote Robust Species Coexistence?
No full textModels on the effects of individual variation often focus on pairwise interactions, but communities could harbor both pairwise and higher order interactions (HOIs). Theoretical studies on HOIs, where a third species modulates pairwise species competition, tend to assign them at random, even though they could be mediated and structured by one-dimensional traits. Here, we consider two different classes of models of both pairwise and higher order trait-mediated interactions: competition alleviated by increasing trait distance, and hierarchical competition where species higher in the hierarchy exert more competition on those lower and vice versa. Combining these models with evolutionary dynamics based on quantitative genetics, we compare their impact on species diversity, community pattern, and robustness of coexistence. Regardless of individual variation, trait-mediated HOIs generally do not promote and often hinder species coexistence, but there are some notable exceptions to this. We present an analytical argument to make sense of these results and argue that while the effects of trait-based HOIs on diversity may appear confusing on the surface, we can understand what outcome to expect in any given scenario by looking at the shape of the effective interaction kernel that arises from the joint action of pairwise and HOI terms. In addition, we find that (i) communities structured by competitive trait hierarchies are highly vulnerable to external perturbations, regardless of HOIs, and (ii) trait-based HOIs with distance-dependent competition create the most robust communities, with minimal impact from individual variation, and (iii) both individual variation and HOIs consistently lead to a more even distribution of species traits than would occur by chance. These findings suggest that trait-mediated HOIs foster coexistence only under special conditions, raising the question of whether HOIs must involve multiple traits to positively affect coexistence in competitive communities.Funding Agencies|Deutsche Forschungsgemeinschaft [BA 7974/1-1]</p
Do Laying Hens Form Stable Social Networks?-A Case Study
No full textA social network is a group of individuals forming a non-random social structure where the number of interactions systematically vary among individuals. The Red Junglefowl, the ancestor of all domesticated chickens, has been shown to form social structures within a larger group; however, how poultry in egg production are socially organised is poorly understood. Egg layers in groups of thousands of individuals are suggested to either, just as Red Junglefowl, form subgroups or to lose social affiliations and replace these with a system of social tolerance. In this case study, a stable group of 20 laying hens with known genetic relationships housed in an outdoor aviary were observed for 3 h per day, during 20 days, in order to determine the social structure in the group. Social affiliations and centralisation measurements were assessed by proximity. The results show that some individuals were consistently more centralised compared to others, which indicates a stable individual variation in sociality. Furthermore, no individual spent more than 10% of her total number of interactions with a particular individual, i.e., little consistency in social affiliations could be found. The results of this case study support the theory of a higher social tolerance rather than a consistent social organisation in domesticated egg layers.Funding Agencies|Lennanders stiftelse; Langmanska stiftelsen</p